K 3500 Truck 4WD V8-454 7.4L VIN J SFI (1996)
Intake Manifold Gasket: All Technical Service Bulletins
Engine - Oil Leak/Weep
File In Section: 6 - Engine
Bulletin No.: 87-61-26
Date: August, 1998
Subject:
Oil Weep at Gasket Between Upper and Lower Intake Manifold (No Repair at this Time)
Models:
1996-99 Chevrolet and GMC C/K, G, P Models
1999 Chevrolet and GMC Medium Duty C Series and Bus Chassis with 7.4L Engine - (VINs B, D, J - RPOs L21, LP4, L29)
Condition
Owners may comment of a weep or leak condition occuring at the gasket between the upper and lower intake manifold.
Cause
During normal operation, the PCV system draws small amounts of oil vapor out of the engine's crankcase. This oil vapor can condense and form a thin
film inside the intake manifold. When this film touches the gasket between the upper and lower intake manifold, it can weep or wick through the gasket.
When enough oil weeps or wicks through the gasket, it may appear that the intake manifold is leaking oil, even though it is not. Also, the area between
the canister purge port and the EGR valve on the intake manifold may appear to have an oil leak. This is caused by the introduction of the PCV into the
upper intake manifold.
Correction
There is currently no repair for this condition. Changing the intake manifold gasket will only provide a very short term fix. Therefore, no attempt to
change the intake manifold gasket should be attempted for this condition. As soon as a fix is developed for this condition this bulletin will be re-issued
with that information.